New York Times (March 7, 2012): Exercising An Aging Brain

More and more retired people are heading back to the nearest classroom - as students and, in some cases, teachers - and they are finding out that school can be lovelier the second time around. Some may be thinking of second careers, but most just want to keep their minds stimulated, learn something new or catch up with a subject they were always curious about but never had time for.

For many, at least part of the motivation is based on widespread reports that exercising the brain may preserve it, forestalling mental decline and maybe even Alzheimer's disease and other types of dementia.

Is there any truth to it? And if there is, what type of learning is best suited to the older brain?

Many studies do find that being mentally active is associated with a lower risk of Alzheimer’s disease. But the standard caveat applies: association does not prove cause and effect, and there is always the chance that the mentally active people who never got Alzheimer’s simply had healthier brains to begin with.

Even, so, researchers say, there is no harm in telling people to try to stay engaged.

“When you and I are having this conversation, you’re taking notes, thinking, remembering pieces of it, trying to relate it to other things,” said Arthur Toga, a professor of neurology and director of the laboratory of neuroimaging at the University of California, Los Angeles. “You’re changing the circuitry in your brain. That is because you have changed something in your brain to retain that memory.”

Dr. Toga elaborated: “The conversation requires nerve cells in the brain to fire, and when they fire they are using energy. More oxygen and sugar must be delivered, by increased blood flow to those regions.

“Why would that be good? If you are vasodilating, delivering more blood to certain regions of the brain, that is important. It increases the longevity and the health of those circuits.